A blind nut consists of a female screw member with female screws formed on the inner surface thereof, a hollow tubular member adjacent to the female screw member, and a flange provided with an opening on one edge of the tubular member. The tubular member of the blind nut is inserted through the mounting hole of the mounted member to cause the flange in contact with the surface of the mounted member; in this state, plastic deformation is performed by utilizing a tightening tool so as to enlarge the diameter of the tubular member, and the mounted member is caused to be sandwiched between the deformed tubular member and the flange. In this manner, the blind nut is fixated onto the mounted member. The male screw provided on a bolt is caused to be engaged with the female screw on the blind nut, which has been fixated onto the mounted member. Then another mounting member can be mounted. When the blind nut is utilized, one side of the mounted member is worked on. Therefore, the blind nut can be utilized to tighten a mounting member such as decorative items and the like onto a member of which the rear side is not accessible (for example, a mounted member such as a panel, and the like).
Generally, when a mounted member is mounted by utilizing a blind nut, the blind nut is caulked to the mounted member, by utilizing a dedicated tool, on the side (blind side) opposite from the insertion side; and then the mounting member is bolted on the insertion side (working side) with a bolt. In order to tighten a mounted member by utilizing a blind nut, two steps have been needed.
Patent Literature 1 relates to such a blind nut as stated above and discloses a caulking nut (blind nut) which comprises a primary nut and a secondary nut. The primary nut is constituted in a manner so that a thick walled-opening member is formed on the upper end of the thin cylindrical member having an inner hole. The thick walled-opening member has a male screw on the outer periphery thereof and has a hole of which the inner diameter is smaller than the inner hole of the thin cylindrical member. On the lower end of the thin cylindrical member, a female screw of which the inner shape is smaller than the inner hole thereof is formed. The secondary nut has a female screw which is capable of being engaged with the male screw provided on the thick walled-opening member, and it is constituted to take a polygonal shape.
In order to mount the caulking nut, the caulking nut is inserted into the mounting hole of the plate (mounted member), with the female screw provided on the secondary nut engaged with the male screw provided on one end of the primary nut. When the screw of the caulking tool is caused to be engaged with the female screw provided on the lower end of the primary nut and pulled into the upper direction, the cylindrical member of the primary nut is bended to the outer side of the radius direction to form a protrusion (expanded radius member), which causes the plate to be sandwiched between the secondary nut and the protrusion of the primary nut. After the caulking tool is removed, a bolt is caused to pass through the mounting hole of the mounting member to be engaged with the female screw of the primary nut. Then, the mounting member such as a frame and the like can be mounted.
When not in use, the secondary nut is loosened to remove it from the primary nut; and the primary nut is pulled out through the mounting hole on the plate. Thus, the caulking nut can be removed.
In utilizing the blind nut stated in Patent Literature 1, the blind nut is caulked by utilizing the caulking tool onto the mounted member on the side opposite from the insertion side, and then the mounting member on the insertion side is screwed by utilizing a bolt. Therefore, the operations need to be conducted in these 2 steps.
Another blind rivet is available which can be mounted in one step by utilizing commercially-available drills and tools. In this blind rivet, the flange is constituted as a separate body, and thus the blind rivet can be removed after it is mounted. However, when the flange is constituted as a separate body from the blind rivet, the strength in the circumferential direction of the enlarged diameter member to be buckled decreases, which may deform the enlarged diameter member into an abnormally deformed shape due to the stress resulting from tightening the screw.
Patent Literature 2 relates to such a blind rivet as stated above and discloses a caulking nut (blind nut) which can be removed after it is mounted; it comprises a primary nut and a washer. On the primary nut, a mouth member having an uneven outer periphery is formed at the upper end of a cylindrical member having a thin inner hole. On the lower end of the cylindrical member, the mouth member has a mating hole which can be mated with the mouth member and has an irregular shape; the outer periphery thereof is constituted into a hexagonal shape.
In order to mount the caulking nut, the caulking nut is inserted into the mounting hole on the plate, with the washer mated with the mouth member provided on the primary nut. A tightening bolt is inserted into the inner hole of the primary nut from the upper direction; the rotary shaft of the caulking tool is mated with the recess of the tightening bolt; and the detent is caused to be engaged with the outer periphery of the hexagonal washer to prevent the washer from rotating around. Thereafter, when the rotating shaft of the caulking tool is rotated to cause the tightening bolt to be screwed into the female screw member and mounted, the cylindrical member of the primary nut is bent in the outward radial direction to form a bulging member, which causes the plate to be clamped between the washer and the bulging member of the primary nut.
When not in use, the tightening bolt is caused to be reversely rotated to remove [the caulking nut] from the primary nut, with the washer retained by the detent to prevent the washer from rotating around. Subsequently, when the washer is pulled out of the upper end of the primary nut, the primary nut can be removed from the plate.
The caulking nut disclosed in Patent Literature 2 is capable of fastening two plates in one bolt-tightening step through the use of the caulking tool by forming a protruding member. Moreover, when the tightening bolt is reversely rotated, and the washer is removed, the caulking nut can be removed. However, when the tightening bolt is mounted to buckle the cylindrical member, force in the circumferential direction is applied to the cylindrical member about the center axis thereof. Meanwhile, in the caulking nut of Patent Literature 2, the washer is constituted as a separate member so as to be removable, the strength against the force in the circumferential direction is decreased. When the tightening bolt is rotated to buckle the cylindrical member, the cylindrical member may be abnormally deformed in a twisted manner. Wherefore, the thickness of the upper portion of the cylindrical member has had to be thick.
Therefore, a blind nut which can be mounted in one step simply by utilizing commercially-available rotating tools such as an electric drill and the like, of which the expanded diameter member is not abnormally deformed, and which can be securely fastened and can be removed after fastening, has been in demand. Registered Utility Model No.: 3121304 and Japanese Unexamined Patent Application Publication No.: 2008-175379 may inform the context of this disclosure.